Differentials for a 78-Year-Old Female with Proximal Tibia Fracture, Pain, and Swelling of the Lower Leg

1. Fracture-Related Differentials (Type of Proximal Tibial Injury)

In elderly women, osteoporotic tibial plateau fractures from low-energy mechanisms (simple falls) are the most common scenario and may be missed on plain films - CT is frequently required.

2. Complications Causing Pain and Swelling (Must Actively Exclude)

a. Acute Compartment Syndrome (ACS) - HIGH PRIORITY

• The most immediately limb-threatening differential
• Tibial plateau fractures (especially bicondylar) carry a significant risk of ACS
• Classic "5 Ps": pain (out of proportion, with passive stretch), pressure (tense compartment), paresthesia, paralysis, pallor
• Diagnosis is clinical +/- intracompartmental pressure measurement
• Requires emergency fasciotomy if confirmed
• Rockwood and Green's Fractures in Adults notes that ACS was more likely in plateau fractures, especially when fracture length exceeded 20% of tibial length

b. Deep Vein Thrombosis (DVT)

• Very high probability in this demographic: elderly, post-fracture, likely immobilized
• Presents with unilateral leg swelling, erythema, warmth, calf/popliteal tenderness
• Fracture-associated DVT can develop rapidly (within 24-48 hours)
• Duplex ultrasound is the investigation of choice
• Must be excluded before attributing all swelling to fracture alone

c. Vascular Injury

• The popliteal artery trifurcates near the proximal tibia; proximal tibial fractures can injure the anterior tibial artery, posterior tibial artery, or peroneal artery
• Assess dorsalis pedis and posterior tibial pulses; if absent or asymmetric, suspect vascular injury
• Ankle-brachial index (ABI) or CT angiography if concern exists
• Cold, pale, pulseless limb indicates ischemia - surgical emergency

d. Peroneal Nerve Injury

• The common peroneal nerve wraps around the fibular neck, in close proximity to the proximal tibia
• Presents with foot drop, sensory loss over dorsum of foot and first web space
• May accompany fibular head fractures or proximal tibial fractures

e. Ligamentous Injury (Knee)

• Proximal tibial fractures are frequently associated with ligamentous disruption
• Consider medial collateral ligament (MCL), lateral collateral ligament (LCL), anterior cruciate ligament (ACL), or posterolateral corner (PLC) injury
• Hemarthrosis on aspiration strongly suggests intra-articular pathology

f. Meniscal Injury

• The tibial plateau fractures commonly involve the menisci (especially lateral meniscus in lateral plateau fractures)
• MRI delineates this, but acute management takes priority over meniscal assessment

3. Non-Fracture Differential Considerations (if fracture mechanism is unclear)

• Septic arthritis / osteomyelitis - fever, elevated CRP/ESR, joint effusion with pyogenic features; rare acutely post-trauma but must be considered
• Gout or pseudogout (CPPD) - crystal arthropathy at the knee; may mimic or co-exist with fracture; look for joint effusion, calcium deposits on X-ray
• Baker's cyst rupture - posterior knee cyst rupture causes sudden calf pain and swelling, mimicking DVT (pseudothrombophlebitis syndrome)
• Cellulitis - skin erythema, warmth, systemic features; may coexist with or follow trauma
• Hemarthrosis without fracture - anticoagulated patients (very common in 78-year-olds) can develop large hemarthrosis from minor trauma

Key Investigations Priorities

1. X-ray (AP, lateral knee) - identify fracture type, Schatzker classification, hemarthrosis
2. CT knee - essential in elderly to characterize fracture complexity, especially when osteoporotic bone obscures detail
3. Duplex ultrasound - exclude DVT
4. Vascular exam / ABI - exclude arterial injury
5. Neurovascular exam - peroneal nerve (foot dorsiflexion, first web space sensation)
6. MRI - if ligament/meniscal injury suspected after acute stabilization
7. Bone scan / MRI - if pathological fracture suspected (underlying malignancy or Paget's)